60 hertz electric fields arising from electric power transmission lines are ubiquitously present in the environment. The strength of such fields varies directly with the operation voltage of the transmission line and inversely with distance from the line. Biological effects attributable to low frequency electric field exposure have recently been described, not withstanding earlier work minimizing the biological significance of such fields. Preliminary results obtained in our laboratory show that a 60 hertz electric field of 150 volts/cm is a biological stressor. That is, field exposure alters normal growth in rats and mice and produces changes in the levels of serum hydroxycorticosterone and serum proteins. This project involves the systematic study of these phenomena in greater detail. Presently, the human health hazard associated with exposure to 60 hertz electric fields is unknown. There have been no systematic studies of such effects and consequently there are no federal or state standards for permissible non-occupationally related exposure. Continuing our initial work, we propose the following experiments to evaluate the biological effects of 60 hertz electric fields at 150 volts/cm: 1. The effect in rats on serum hydroxycorticosterone, triglycerides, total proteins and the effect on growth, tissue structure and food and water consumption. 2. The effect on reproduction in mice. 3. The effect in rabbits of acute and chronic exposure. The experiments will be repeated as a function of field strength and frequency.